The invention relates to tires, especially to metal tire cords which reinforce the belts of radial or bias-belted tires.
U.S. Pat. Nos. 4,022,009; 4,176,513 and 4,258,543 are typical of the many patents that relate to metal tire cords that are composed of a number of round, metallic filaments or wires which are helically twisted together. U.S. Pat. No. 3,794,097 describes a single flat wire that can be used to reinforce a tire. In an article titled, `Tire Cord Materials For the Belted Bias Tire`, appearing in the April 1973 issue of Chemical Engineering Progress, there is a statement regarding the steel filaments of wire tire cords that, "These filaments are twisted together in groups of as few as three filaments to as many as 50, covering the wide range of strength to meet the tire performance requirements of everything from the smallest passenger tire to the giant earth mover." Thus, it is known to reinforce a tire with single, flat wires, or cords which are composed of at least three round metallic filaments which are twisted together.
In recent years, the automobile industry has undergone a radical change with the emphasis on smaller and lighter cars to obtain better gasoline mileage to reduce the consumption of one of our most valuable natural resources, petroleum. Tires play an important role in this change, because the resistance of tires to rolling along the roadway has a decided effect on the mileage and gasoline consumption of the vehicle. The rolling resistance of a tire is dependent on the flexibility of the tire as it moves through the footprint, or contact the roadway. Large tire cords composed of many filaments, are naturally more inflexible than smaller cords, and require more rubber to cover them to produce a heavier and stiffer tire with greater rolling resistance. The invention is directed to the provision of a small, highly flexible tire cord which, when used in the belts of a radial or bias-belted tire, decreases the rolling resistance of the tire to increase automobile mileage per gallon of gasoline.